HONEYMOON killer Gabe Watson will fly out of Brisbane today hours after being released from jail.

Watson, 33, was released from the Borallon jail, west of Brisbane, at 6.30am (AEST) today.

The former bubblewrap salesman served 18 months for the manslaughter of his wife Tina, who drowned during a honeymoon scuba dive in north Queensland in 2003.

Upon his release from jail, Watson was immediately taken into the custody of immigration officials and whisked to the Brisbane airport.

A David Gabriel Watson, Gabe Watson's given name, was booked to leave Brisbane domestic airport at 11.55am (AEST) on flight QF 619, arriving in Melbourne's Tullamarine airport at 3.15pm (AEDT).

He will be taken to the Maribyrnong Immigration Detention Centre in Melbourne, where he will await deportation.

A cloud hangs over the timing of Watson's expected deportation, with his solicitor saying it could take months.

The Australian Government wants an assurance from US Attorney-General Eric Holder that Watson will not face the death penalty if tried and convicted in his home state of Alabama which wants to try him for murder and kidnapping.

Alabama Attorney-General Troy King earlier this year promised prosecutors would seek a life sentence without parole, but the Australian Government says it needs the assurance from the US federal authorities.

Federal Attorney-General Robert McClelland said a report in The Australian newspaper saying Australian officials had asked Watson to sign his own "death warrant" - a statement acknowledging he may be executed on returning to the US - was "outrageous".

The immigration department had advised Watson of the possible consequences if he returned to the US voluntarily, Mr McClelland said.

On the basis of that advice, he had decided not to voluntarily return to the US and would not be deported until Australia had an assurance he would not face the death penalty, he said.

"I think that story, how it's been framed, and the imputations made against officers of the (immigration) department was really quite outrageous," Mr McClelland told ABC Radio today.